Topic: C3 1 The Periodic Table
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C3.1 The periodic table
The modern periodic table has been developed from work begun by Newlands and
Mendeleev. There are trends in chemical properties within the periodic table linked to
how easily the element gains or loses electrons.
You should use your skills, knowledge and understanding to:
 Evaluate the work of Newlands and Mendeleev in terms of their contributions to the
development of the modern periodic table.
 Explain why scientists regarded a periodic table of the elements first as a curiosity,
then as a useful tool and finally as an important summary of the structure of atoms.
C3.1.1 The early periodic table
a) Newlands, and then Mendeleev, attempted to classify the elements by arranging them
in order of their atomic weights. The list can be arranged in a table so that elements
with similar properties are in columns, known as groups. The table is called a periodic
table because similar properties occur at regular intervals.
b) The early periodic tables were incomplete and some elements were placed in
inappropriate groups if the strict order of atomic weights was followed. Mendeleev
overcame some of the problems by leaving gaps for elements that he thought had not
been discovered.
C3.1.2 The modern periodic table
a) When electrons, protons and neutrons were discovered early in the 20th century, the
periodic table was arranged in order of atomic (proton) numbers. When this was done,
all elements were placed in appropriate groups.
b) The modern periodic table can be seen as an arrangement of the elements in terms of
their electronic structures. Elements in the same group have the same number of
electrons in their highest occupied energy level (outer shell).
You should understand that the number of electrons in the highest occupied
energy level (outer shell) for elements in the main groups is equal to the group
number.
Darwen Vale High School Science Department 2013
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Topic: C3 1 The Periodic Table
Date
Name:
Specification Content
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Comments
C3.1.3 Trends within the periodic table
a) The elements in Group 1 of the periodic table (known as the alkali metals):
 Are metals with low density (the first three elements in the group are less dense
than water).
 React with non-metals to form ionic compounds in which the metal ion carries a
charge of +1. The compounds are white solids that dissolve in water to form
colourless solutions.
 React with water, releasing hydrogen.
 Form hydroxides that dissolve in water to give alkaline solutions.
b) In Group 1, the further down the group an element is:
 The more reactive the element.
 The lower its melting point and boiling point.
c) Compared with the elements in Group 1, transition elements:
 Have higher melting points (except for mercury) and higher densities.
 Are stronger and harder.
 Are much less reactive and so do not react as vigorously with water or oxygen.
d) Many transition elements have ions with different charges, form coloured compounds
and are useful as catalysts.
e) The elements in Group 7 of the periodic table (known as the halogens) react with
metals to form ionic compounds in which the halide ion carries a charge of –1.
f) In Group 7, the further down the group an element is:
 The less reactive the element.
 The higher its melting point and boiling point.
g) A more reactive halogen can displace a less reactive halogen from an aqueous
solution of its salt.
h) The trends in reactivity within groups in the periodic table can be explained because
the higher the energy level of the outer electrons: (HT only)
 The more easily electrons are lost.
 The less easily electrons are gained.
Darwen Vale High School Science Department 2013
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